The objective of the proposed resarch is to characterize the interaction of the polycyclic aromatic hydrocarbon (PAH) benzo(a)pyrene with histone and nonhistone chromosomal proteins (NHCP). Analyses will be carried out with both a model target (calf thymus nuclei) and with a well characterized carcinogen transformable cell line. In the model system,, BP will be converted to reactive metabolites employing a NADPH dependent rat liver microsomal-activating system. The covalent binding of BP to both histone and NHCP will be characterized utilizing high resolution analytical techniques. Particular attention will be directed at histone 1 (H1), which, based on preliminary experiments, represents the principal histone target of covalent BP binding. The possible restricted binding distribution of BP to H1 subfractions and the localization of BP in the primary structure of H1 (utilizing chemical modification, restricted proteolysis and N terminal sequencing approaches) will be examined. The effect of BP binding on the association of both histones and NHCP with double-stranded DNA as well as histone 1 with NHCP will be studied using affinity chromatography. Concurrent studies initially will examine BP-chromosomal protein interactions with the M2 cell line and compare the covalent binding of BP to that of BP 4,5-oxide, a non carcinogenic analog. The binding of BP also will be compared in a transformable vs. a non transformable cell line. It is anticipated that the proposed studies will yield valuable insights into those chromosomal protein target(s) (interactions) which may be essential components of malignant transformation(s) induced by PAH carcinogens.